The invention relates to a dart. In particular a dart for use with animals or humans.
Animal syringe darts exist for the specific purpose of remotely injecting substances (eg a tranquilliser) into animals. Such a system is necessary in every case where it is not possible to either physically capture and handle the animal or to administer substances by other indirect means (eg orally).
Existing systems differ with respect to two components:
1) The mechanism used to inject the substance; and
2) The mechanism used to bring the syringe into contact with the animal.
Current injection mechanisms all have certain disadvantages.
Chemical reaction mechanisms rely on the mixture of reactants at the time of impact to create carbon dioxide expanding the delivery chamber and effecting injection. The most common system used is the pre-pressurised mechanism. The disadvantages of this system are that the apparatus must remain pressurised until the moment of impact (they often leak). Further, the pre-pressurised dart may accidentally discharge and inject a non target being.
Detonation mechanisms are too traumatic on anything other than very large animals, can cause considerable tissue damage and are often non-reusable and expensive.
Hand driven mechanisms used in a pole are restricted to the length of the pole. The dissolution/absorption mechanism involves a slow delivery of the substance to the animal""s circulatory system limiting its application. Hand thrown mechanisms are the most basic and least effective methods.
There are several known barrel based mechanisms such as blow pipes which are only effective at short range (5 m or less) and compressed air powered mechanisms which are only accurate to a range of 20 meters. If the compressed air mechanism uses pressurised carbon dioxide its effectiveness will vary according to the ambient temperature as well. Cartridge powered systems involve considerable forces and the system can end up quite complex with a number of adjustments required for each shot, creating a considerable margin for error. The system is also very noisy and the first shot usually disperses the target animals.
In summary, the barrel based mechanisms suffer from errors associated with variation in delivery pressures and the barrel limits the size of the syringe. The syringe used is also limited by the forces and temperatures of the barrel system. In dense scrub, these syringes can also be easily lost. Further the force with which the syringe is shot is such that the syringe may be damaged either leaving the barrel or as a result of the impact with the animal. Such systems are also not readily suited to use with wild animals. The sound of the shot is heard by the animal before the syringe reaches the animal and therefore the syringe may miss.
It would also be useful if animal syringe darts were available which could take samples of blood or tissue.
In the following description and in the claims reference is made to xe2x80x9ctubular membersxe2x80x9d. It will be understood by those skilled in the art that this term is meant to define an elongated member of substantially constant cross-section which may or may not be circular. The term envisages any cross-sectional shape such as oval, rectangular or triangular.
It is an object of the present invention to provide an animal dart which may be projected from devices other than fire arms e.g. from crossbows or bows.
The invention is based upon the use of momentum absorption. In this system, the impact momentum is utilized by the apparatus. This system is more reliable as it only requires impact energy to effect injection or sampling. It is also superior to conventional systems in that a considerable reduction in force results from the absorption of impact momentum. This results in a less traumatic impact and a more consistent injection or sampling event.
According to a first form of the invention, a dart for administering an injection fluid to an animal is provided comprising:
(a) a tubular member having a front end closed by a penetrable closure;
(b) a syringe located within and movable longitudinally along the tubular member, the syringe having:
(i) a barrel to receive injection fluid;
(ii) a hollow needle extending from one end of the barrel towards the penetrable closure of the front end;
(iii) a closure at the other end of the barrel;
(iv) a plunger located in the barrel which is in sealing engagement with and movable along the barrel towards or away from the needle; and
(v) an aperture or passageway in or extending from the barrel rearward of the plunger in its loaded position communicating between the tubular member and an area in the barrel rearward of the plunger; and
(c) sealing means mounted on the syringe rearward of the aperture or passageway and sealingly engaging the tubular member to seal the syringe within the tubular member,
wherein upon impact of the dart, the syringe is caused to move in a forward direction in the tubular member, the pressure in the tubular member between the penetrable closure and the sealing means increases until the needle penetrates through the closure; at the same time the pressure behind the plunger is increasing due to the passage of air through the aperture or passageway so that when the needle penetrates the closure the pressure differential between the area behind the plunger and the area in front of the hollow needle causes the injection fluid to be expelled.
In a preferred form of the invention, the barrel further includes a one way valve interposed between the plunger and the aperture or passageway. This one way valve permits air to pass into the area between the valve and the plunger but does not permit air to escape therefrom towards the aperture or passageway. In this preferred form, rebounding of the dart or leakage of air from the dart upon impact does not adversely effect the injection pressure applied to the plunger.
In another embodiment of the invention, the barrel is a pair of concentric tubes and the sealing means is interposed between the outer barrel and the tubular member. The concentric tubes define the passageway therebetween which communicates between the tubular member and the area rearward of the plunger.
Preferably, the tubular member has a separate tail section. In this embodiment, the momentum from the tail section is transferred directly to the plunger.
Preferably, the rear end of the tubular member has a rear vent. More preferably, the rear vent further includes a one-way valve to allow air to enter the tubular member. In this embodiment, the rear vent allows air to enter behind the syringe and thus prevents a vacuum forming which would adversely affect the injection pressure.
Upon impact with the target, the tubular member rapidly slows down, being at a much faster deceleration rate than that of the syringe causing the syringe to move toward the front end. This movement increases the pressure prevailing in the chamber between the sealing means and the penetrable closure. The continued movement of the syringe causes the needle to pierce the closure and by differential pressure, the injection fluid is injected into the target.
According to a second form of the invention, a dart for taking a sample from an animal is provided comprising:
(a) a tubular member having a front end closed by a penetrable closure and a rear end closed by an airtight closure;
(b) a syringe located within and movable longitudinally along the tubular member, the syringe having:
(i) a barrel to receive a sample;
(ii) a hollow needle extending from one end of the barrel towards the penetrable closure of the front end;
(iii) a closure at the other end of the barrel;
(iv) a plunger located in the barrel which is in sealing engagement with and movable along the barrel towards or away from the needle; and
(v) an aperture or passageway in the barrel rearward of the plunger communicating between the tubular member and an area in the barrel rearward of the plunger; and
(c) sealing means mounted on the syringe between the plunger and the aperture or passageway and sealingly engaging the tubular member to seal the syringe within the tubular member and inhibit air moving from the area about the needle to the area rearward of the sealing means,
wherein upon impact of the dart, the syringe is caused to move in a forward direction in the tubular member, the pressure in the tubular member between the sealing means and the area rearward of the sealing means decreases until the needle penetrates through the closure; so that when the needle penetrates the closure the pressure differential between the area behind the sealing means and the area in front of the hollow needle causes the plunger to move towards the rear end of the tubular member to draw a sample through the needle into the barrel.
Preferably, the barrel further includes a one way valve interposed between the plunger and the aperture or passageway. This one way valve permits air to pass out of the area between the valve and the plunger but does not permit air to enter therefrom the aperture or passageway. In this preferred form, rebounding of the dart or leakage of air from the from the rear end airtight closure does not adversely effect the injection pressure applied to the plunger.
Preferably, the tubular member is formed as the bolt of an arrow, in which case it is provided with a set of outwardly directed vanes located at or adjacent the other end of the tubular member. In this embodiment when the arrow is projected the force applied to the syringe biases it initially towards the rear of the arrow.
The needle assembly is conventional in the sense that it is hollow and permits injection fluid to pass through it from the barrel. Preferably, the needle may additionally include ancillary means or be of enlarged bore to house a tag or solid implant materials or receive tissue samples. For example, it may be possible to include solid hormonal materials. In this arrangement, it would also be possible to select antiseptic fluid as the injection material to clean the implanted area simultaneously with the implanting action.
The penetrable closure may be fabricated from any material which can maintain the requisite pressure conditions yet be penetrated by conventional syringe needles.
The sealing means may be, for example, O-rings.
In a preferred embodiment, the syringe has a pleat with a smaller radius about the middle of the length of the barrel. The pleat prevents the plunger from moving past the pleat and thus maintaining the separation between an area in front of the pleat which will contain the injection fluid or receive the sample and the area rearward of the pleat.
In a preferred embodiment, the front end of the tubular member contains a nose plug which once the needle has passed through the penetrable closure receives the front end of the syringe and prevents it from moving further forward.
In a preferred embodiment, the syringe has radial detents on its inner wall. The detents prevent the closure in the syringe from moving past the radial detents.
Additionally the dart may include a breakable pocket associated with the penetrable closure to hold additional fluid to be applied to the target. For example, the pocket may contain dye so it will be readily apparent which targets have been treated or impacted by the dart.
In the arrow type embodiment of this invention, it is expected that the most suitable propulsion device will be a cross bow. These are strong, very accurate and essentially silent. This last feature is particularly important as animals will not be initially scared into movement.
In another embodiment of the invention, the dart is used in combination with a handle or other applications device adapted to cause the syringe of the dart to move forward and the needle to penetrate through the closure. In this arrangement the device will have an end which has a bore less than that of the tubular member.
According to a third form of the invention, there is provided a syringe for a tubular dart for administering an injection fluid to an animal comprising:
(a) a barrel to receive the injection fluid;
(b) a hollow needle extending from one end of the barrel;
(c) a closure at the other end of the barrel;
(d) a plunger located in the barrel which is in sealing engagement with and movable along the barrel towards or away from the needle;
(e) an aperture or passageway in or extending from the barrel rearward of the plunger in its loaded position communicating between an outer surface of the syringe and an area in the barrel rearward of the plunger; and
(f) sealing means mounted on the syringe rearward of the aperture or passageway to sealingly engage the tubular dart.
According to a fourth form of the invention, there is provided a syringe for a tubular dart for taking a sample from an animal comprising:
(a) a barrel to receive the sample;
(b) a hollow needle extending from one end of the barrel;
(c) a closure at the other end of the barrel;
(d) a plunger located in the barrel which is in sealing engagement with and movable along the barrel towards or away from the needle;
(e) an aperture or passageway in the barrel rearward of the plunger in its loaded position communicating between an outer surface of the syringe and an area in the barrel rearward of the plunger; and
(f) sealing means mounted on the syringe between the plunger and the aperture or passageway to sealingly engage the tubular dart.
Whilst it is anticipated that this dart will have principal applications with animals, it is equally adapted to use with humans.
The main significance of the dart of the invention is that the syringe becomes operable under the influence of its own momentum. This means, amongst other things, that:
the dart may be carried and stored both safely and indefinitely (injection fluid permitting), and it is not possible for it to inject anything without the use of a projecting mechanism;
the absorption of momentum inhibits bounce of the dart upon impact and subsequent failure to inject;
the absorption of momentum enables the projecting mechanism to fire the dart at higher velocity than would otherwise be possible which results in a consequent flatter and more accurate trajectory; and
the absorption of momentum enables sensitive devices such as electronic tracking devices which may otherwise malfunction under the influence of excessive forces which are applied upon firing, to be fitted inside the dart.
Further, the needle may be encased (and protected) within the tubular member and therefore maintains its condition and sterility.